Prior art self-propelled robots are known which operate electrically and comprise tools for the treatment of surfaces (by way of example, brushes, cutting blades or the like) sometimes associated with a circuit for extracting debris or various impurities.
Known self-propelled robots also comprise movement means, by way of example wheels, tracks and the like, having specific shapes and dimensions on the basis of the predetermined scope of use.
Generally, the movement means and/or the tools of the self-propelled robot are connected to their respective electric motors by a mechanical power transmission, for example direct keying on the shaft of the motor or by interposed gear wheels for changing the transmission ratio between drive shaft and motor-driven wheel and/or impeller.
A self-propelled robot suitable for cleaning the surfaces of a swimming pool is illustrated by way of an example in document EP 2554764A1.
Generally, the above-mentioned electric motor is hermetically isolated from the outside and housed in a protective and structural shell and protrudes on the outside, by a sealed joint or a sealing gasket, only by the portion relative to the hub to couple with the wheels for the movement of the robot and/or with a tool of the robot. In other words, the known self-propelled robot has at least one mechanical power transmission which puts the inner part (a motor element) of the protective shell in contact with an external part (driven element) of the protective shell.
It is known that the sealed joint and/or the sealing gasket are elements of the robot that are subject to wear over time, both due to corrosion due to humidity/water and due to the depositing of any debris at the mechanical power transmission, for example between the shaft of an electric motor and a respective hermetic seal of the transmission, thus often compromising the overall hermetic seal of the robot.
Restoring the seals and replacing the worn elements requires complex maintenance that also involves manual intervention by a skilled technician. Moreover, even the smallest water infiltration inside the protective shell of a self-propelled robot may adversely affect the electronic circuits and the connections of the electrical cables contained inside, thus compromising its operation.
It should also be noted that following maintenance of the robot where it was necessary to open the protective shell even partly, the impermeable seals must be restored again by applying sealing mastics on the edges and stops of the shell, which requires skilled labour by a technician and hardening and curing times involving increased maintenance costs.